Radiological imaging is acknowledged to be of value for the dental practitioner, helping to identify various problems and to validate other measurements and observations related to the patient's teeth and supporting structures. Among x-ray systems with particular promise for improving dental care is the extra-oral imaging apparatus that is capable of obtaining one or more radiographic images in series and, where multiple images of the patient are acquired at different angles, combining these images to obtain a 3-D reconstruction showing the dentition of the jaw and other facial features for a patient. Various types of imaging apparatus have been proposed for providing volume image content of this type. In these types of systems, a radiation source and an imaging detector, maintained at a known distance (e.g., fixed or varying) from each other, synchronously revolve about the patient over a range of angles, taking a series of images by directing and detecting radiation that is directed through the patient at different angles of revolution. For example, a volume image (e.g., reconstruction of 3D or volume images) that shows the shape and dimensions of the head and jaws structure can be obtained using computed tomography (CT), such as cone-beam computed tomography (CBCT), or other volume imaging method. The resulting volume images are acknowledged to be of particular value for obtaining useful information for assisting diagnosis and treatment.
Before an orthodontic treatment, it is current practice to create a virtual 3D model of the upper and lower patient's jaw. The virtual teeth are then segmented and can be displaced relative to each other to simulate an orthodontic treatment plan. More than one technique can be used to acquire a 3D model of teeth. First the patient's mouth can be scanned using an intra oral camera that acquires a plurality of frames before reconstructing the 3D model. Positive physical casts representing the patient's lower and upper jaw can also be scanned by the intra oral camera. Alternatively, the two positive physical casts representative of the mandible and the maxillary of the patient can be separately scanned using a CBCT x-ray device. A CBCT device can include a gantry supporting an X-ray source and a sensor opposing each other that rotates about a plaster scan positioned a support. A plurality of 2D frames is acquired by the sensor during the rotation. A 3D matrix of grey levels is reconstructed using some standard algorithms.
A crucial point is to register the lower and the upper jaw virtual models in actual occlusion conditions. Indeed, obtaining a good occlusion registration of the upper and the lower teeth models is one necessary condition for a good assessment of the initial conditions of the patient teeth before starting an orthodontic treatment.
It can be appreciated that there is still a need for dental x-ray imaging apparatus and/or methods that can provide a cheaper, rapid, and/or accurate assessment of initial conditions including occlusion registration of the upper and the lower teeth of a patient.